### Home > APCALC > Chapter 10 > Lesson 10.3.1 > Problem10-138

10-138.

Multiple Choice: A function that satisfies the differential equation $f^\prime(x) + f(x) = 0$ is: Homework Help ✎

1. $f(x) = \sin (x)$

1. $f(x) = \cos (x)$

1. $f(x) = e^x$

1. $f(x) = e^{−x}$

1. $f(x) = \ln (x)$

$\frac{dy}{dx}+y=0$

$dy=-ydx$

$\frac{dy}{y}=-dx$

$\text{Integrate: }\ln|y|=-x+C$

$y=Ce^{-x}$